Electric knife switches with simplified contact pressure adjustament



March 1966 G. SlVlY 3,240,911

ELECTRIC KNIFE SWITCHES WITH SIMPLIFIED CONTACT PRESSURE ADJUSTMENT Filed May 18, 1962 fl @'a@ i I i .{L-IS' Fig. 4 l4 WITNESSES INVENTOR George Siviy W M) BY 7514 WW Mim/AA ATTORNEY United States Patent 3,240,911 ELECTRIC KNlFE SWITCHES WITH SIMPLIFIED QONTACT PRESSURE ADJUSTMENT George rviy, Monroeville, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., :1 corporation of Pennsylvania Filed May 18, 1962, Ser. No. 195,838 4 Claims. (Cl. 200-162) This invention relates, generally, to electrical switches and, more particularly, to switches of the knife-blade type suitable for carrying relatively large amounts of current.

In switches of the knife-blade type it is important that the contact portions of the blades make good contact with the stationary hinge and break contact members. Heretofore, it has been customary to utilize cup washers drawn together with a bolt and nut to obtain the desired contact pressure. Since the design of the cup washer permits relatively little deflection as a spring member, loading and adjustments are critical. During the operation of knife-blade switches employing cup washers, wear on the contact portions of the switches makes periodic readjustment of the cup washers necessary to obtain proper contact pressure. Readjustment of contact pressure, necessary to compensate for Wearing of parts is ditficult since a fraction of a turn of the nut increases the contact pressure considerably.

An object of this invention is to provide a switch of the knife-blade type which does not require the use of cup washers to obtain contact pressure between the contact members of the switch.

A more specific object of the invention is to provide for utilizing long lever arms as spring members to maintain contact pressure between the contact members of a switch.

Another object of the invention is to provide a switch having a relatively large range of adjustment of contact pressure.

A further object of the invention is to compensate for misalignment of the blades of a switch.

Still another object of the invention is to provide for readily adjusting the contact pressure of a knife-blade switch.

A more general object of the invention is to provide a knife-blade switch which is simple in operation and which may be economally manufactured and installed.

Other objects of the invention will be explained fully hereinafter or will be apparent to those skilled in the art.

In accordance with one embodiment of the invention, two generally parallel spaced blades of a switch are composed of zirconium copper which has a high electrical conductivity and mechanical resistance to bending, or stifiness, thereby making it applicable for current carrying spring members. Rotatable studs are threaded into the blades between the hinge contact member and the break contact member for drawing the blades together, thereby utilizing the spring characteristics of the blades to obtain the desired contact pressure between the contact members of the switch. Compensation for misalignment of the blades is obtained by brazing silver buttons on the sides of the blades adjacent the hinge contact and the break contact. The buttons have spherical surfaces which engage the sides of the hinge contact member and the break contact member.

3,240,911 Patented Mar. 15, 1966 ice For a better understanding of the nature and objects of the invention, reference may be had to the following detailed description taken in conjunction with the accompanying drawing, in which:

FIGURE 1 is a view, in plan, of a disconnect switch embodying the principal features of the invention;

FIG. 2 is a view, in side elevation, of the switch shown in FIG. 1;

FIG. 3 is a view, in plan, of a modified hinge structure for the switch; and FIG. 4 is a view, in side elevation, of the hinge shown in FIG. 3.

Referring to the drawing, and particularly to FIGS. 1 and 2, the disconnect switch shown therein comprises a hinge contact member 11, a break contact member 12 spaced from the hinge member 11 and two.spaced, generally parallel blades 13 pivotally mounted on the hinge member 11 and engaging the break member 12 when the switch is closed. The hinge member 11 has a base 14 and an upright portion 15. Likewise, the break member 12 has a base 16 and an upright portion 17. The bases 14 and 16 may be attached to a suitable supporting structure (not shown).

As shown more clearly in FIG. 1, the two blades 13 are disposed on opposite sides of the upright portions 15 and 17 of the hinge member 11 and the break member 12, respectively. The blades are pivotally attached to the upright portion 15 by a pin 18 which is retained in position by a cotter -key 19. When the switch is closed, the blades 13 engage opposite sides of the upright portion 17 of the break contact member 12, thereby completing an electric circuit through the switch. It will be understood that power conductors may be connected to the base portions 14 and 16 of the hinge member 11 and the break member 12, respectively.

In order to compensate for misalignment of the blades 13, a plurality of contact buttons or members 21 are secured to the inner surfaces of the blades. The members 21 may be composed of silver, or other suitable material, and they may be attached to the blades by brazing, or other satisfactory method. Each contact member 21 has a generally spherical surface for engaging one side of the upright portion 15 of the hinge contact member 11 or the upright portion 17 of the break contact member 12, thereby maintain good contact between the contact members of the switch even though the parts of the switch may be slightly out of alignment.

With a view to maintaining the desired contact pressure between the contact members of the switch without utilizing cup washers, the blades 13 are preferably composed of zirconium copper which is a copper base alloy having a high electrical conductivity and sufi'icient mechanical stifiness, or resistance to bending, to permit, the blades to be utilized as current carrying spring members. As shown in FIGS. 1 and 2, two adjusting studs 22 are threaded into the blades 13 between the hinge member 11 and the break member 12. Each stud 22 has right and left hand threads 45 and 47, respectively, thereby drawing the two blades together as the studs are rotated and maintaining a predetermined lateral spacing between the blades 13 adjacent to each stud 22. In this manner the spring characteristic of the blades is utilized to obtain the desired contact pressure between the contact members of the switch. Lock nuts 23 are provided on the studs to retain them in proper adjustment. The studs may be easily readjusted to compensate for wear of the contact members, thereby maintaining the correct contact pressure between the contact members of the switch.

Also, the studs provide a rigid blade construction which with the stabilizing effect of the four contact members 21 equally spaced around the pivot pin 18 make a satisfactory hinge joint. Since the necessary contact pressure is obtained by the spring action of the blades, no cap washers or other means of obtaining contact pressure are required.

The blades 13 may be operated in a manner well known in the art, as by means of an actuating lever 29 attached to the blades. If desired, a latch (not shown) of a type also well known in the art may be provided for retaining the blades in the closed position. The latch may be operated by means of a hook stick (not shown).

An alternate hinge construction is shown in FIGS. 3 and 4 in which each blade 13' has two integral contact fingers 24 which extend beyond a shouldered stud 25 mounted in the upright portion of the hinge member 11 having a base 14. Each finger 24 has a contact button or member 21 having a spherical surface for engaging a side of the upright portion 15. A nut 26 may be tightened on the threads A aand 25B the stud 25 to draw the blades 13 against shoulders 27 on the stud, thereby deflecting the blades to obtain the desired contact pressure between the contact members because of the spring characteristic of the zirconium copper blades. A washer 28 composed of anti-friction material, such as Teflon may be provided between each blade and the upright member 15 to reduce friction. It will be understood that an adjustable stud, like one of the studs 22 shown in FIGS. 1 and 2, may be utilized to obtain the desired contact pressure between the blades 13' and the break contact member which is not shown in FIGS. 3 and 4.

The alternate construction shown in FIGS. 3 and 4 has the additional advantage that the operation of the hinge provided is independent of or unaffected by the spring characteristics of the contact blades. This arrangement avoids any relative lateral movement of the contact blades 13 outside the normal plane of operation during opening or closing of the switch shown in FIGS. 3 and 4.

From the foregoing description it is apparent that the switch structure incorporates relatively long lever arms for spring members. This results in greater deflection at a given load. Therefore, variations in deflection due to manufacturing tolerances and from operational wear are not critical. The electrical conductivity and mechanical stiffness or spring characteristic of the zirconium copper blades enables them to be utilized as current conducting spring members, thereby making it possible to eliminate cup washers, which have undesirable characteristics, from the switch structure.

Since numerous changes may be made in the abovedescribed construction and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. An electrical switch comprising a hinge contact member, a break contact member spaced from the hinge contact emmber, two spaced generally parallel blades pivotally attached to the hinge contact member and engaging the break contact member when the switch is closed, said blades being composed of a material having high electrical conductivity and mechanical stifl ness, rotatable, adjustable means threaded into said blades and extending laterally between the blades for drawing the blades together between the hinge contact member and the break contact member and for maintaining a determined lateral spacing between the blades adjacent to the adjustable means, thereby utilizing the blades as spring members to maintain contact pressure between the blades and the hinge contact member and the break contact member, and spaced contact members secured to the sides of the blades adjacent to the hinge contact member and to the break contact member, said spaced contact members having generally spherical surfaces for engaging the surfaces of the hinge contact member and the break contact member, the contact pressure between said blades and the hinge contact member being maintained by the adjustable means independently of the position of said blades with respect to the break contact member.

2. An electrical switch comprising a hinge contact member, a break contact member spaced from the hinge contact member, two spaced generally parallel blades pivotally attached to the hinge contact member and engaging the break contact member when the switch is closed, said blades being composed of a material having high electrical conductivity and a spring characteristic, adjustable means threaded into and extending laterally between said blades intermediate the hinge contact member and the break contact member with right and left hand threads to maintain a predetermined lateral spacing between the blades adjacent to the adjustable means and to draw the blades together to utilize the spring characteristic of the blades to obtain a desired contact pressure between the blades and the hinge and break contact members of the switch, and spaced contact members secured to the sides of the blades adjacent to the hinge contact member and to the break contact member, said spaced contact members having generally spherical surfaces for engaging the surfaces of the hinge contact member and the break contact member, the contact pressure between said blades and the hinge contact member being maintained by the adjustable means independently of the position of said blades with respect to the break contact member.

3. An electrical switch comprising a hinge contact member, a break contact member spaced from the hinge contact member, two spaced generally parallel blades pivotally attached to the hinge contact member and engaging the break contact member when the switch is closed, said blades being composed of zirconium copper having high electrical conductivity and a spring characteristic, and adjustable means for drawing said blades together between the hinge contact member and the break contact member to utilize the stiffness of the blades to maintain contact pressure between the blades and the hinge contact member and the break contact member, said adjustable means including means secured to both blades and extending laterally between the blades for maintaining a predetermined lateral spacing between the blades adjacent to the adjustable means, the contact pressure between said blades and the hinge contact member being maintained by the adjustable means independently of the position of said blades with respect to the break contact member, and silver contact members secured to the sides of the blades adjacent the hinge contact member and the break contact member, said silver contact members having generally spherical surfaces for engaging the hinge contact member and the break contact member.

4. An electrical switch comprising a hinge contact member, a break contact member spaced from the hinge contact member, two spaced generally parallel blades pivotally attached to the hinge contact member and engaging the break contact member when the switch is closed, said blades being composed of a material having high electrical conductivity and mechanical stiffness, and adjustable means for drawing said blades together between the hinge contact member and the break contact member to utilize the stiffness of the blades to maintain contact pressure between the blades and the hinge contact member and the break contact member, said adjustable means including means secured to both blades and extending laterally between the blades for maintaining a predetermined lateral spacing between the blades jacent to the adjustable means, the contact pressure be- 3,240,911 5 6 tween said blades and the hinge contact member being References Cited by the Examiner maintained by the adjustable means independently of the position of said blades with respect to the break contact UNITED STATES PATENTS member, and spaced contact members secured to the 2,353,287 11/1944 B ayer 200-170 sides of the blades adjacent the hinge contact member 5 2,546,366 3/1951 Lmdae 200170 and the break contact member, said spaced contact Inem- 2,907,856 10/1959 Ballou 200 170 bers having generally spherical surfaces for engaging the surfaces of the hinge contact member and the break con- ROBERT SCHAEFER Actmg Pnmary Examiner tact member. BERNARD A. GILHEANY, Examiner. 

1. AN ELECTRICAL SWITCH COMPRISING A HINGE CONTACT MEMBER, A BREAK CONTACT MEMBER SPACED FROM THE HINGE CONTACT MEMBER, TWO SPACED GENERALLY PARALLEL BLADES PIVOTALLY ATTACHED TO THE HINGE CONTACT MEMBER AND ENGAGING THE BREAK CONTACT MEMBER WHEN THE SWITCH IS CLOSED, SAID BLADES BEING COMPOSED OF A MATERIAL HAVING HIGH ELECTRICAL CONDUCTIVITY AND MECHANICAL STIFFNESS, ROTATABLE, ADJUSTABLE MEANS THREADED INTO SAID BLADES AND EXTENDING LATERALLY BETWEEN THE BLADES FOR DRAWING THE BLADES TOGETHER BETWEEN THE HINGE CONTACT MEMBER AND THE BREAK CONTACT MEMBER AND FOR MAINTAINING A DETERMINED LATERAL SPACING BETWEEN THE BLADES ADJACENT TO THE ADJUSTABLE MEANS, THEREBY UTILIZING THE BLADES AS SPRING MEMBERS TO MAINTAIN CONTACT PRESSURE BETWEEN THE BLADES AND THE HINGE CONTACT MEMBER AND THE BREAK CONTACT MEMBER, AND SPACED CONTACT MEMBERS SECURED TO THE SIDES OF THE BLADES ADJACENT TO THE HINGE CONTACT MEMBER AND TO THE BREAK CONTACT MEMBER, SAID SPACED CONTACT MEMBERS HAVING GENERALLY SPHERICAL SURFACES FOR ENGAGING THE SURFACES OF THE HINGE CONTACT MEMBER AND THE BREAK CONTACT MEMBER, THE CONTACT PRESSURE BETWEEN SAID BLADES AND THE HINGE CONTACT MEMBER BEING MAINTAINED BY THE ADJUSTABLE MEANS INDEPENDENTLY OF THE POSITION OF SAID BLADES WITH RESPECT TO THE BREAK CONTACT MEMBER. 